Different types of sensor elements for recording at least one property of a fluid medium are available in the related art. The present invention is described in the following with reference to pressure-based mass airflow meters. However, other embodiments are also possible.
To determine the air mass in air systems, such as in the induction tract of an internal combustion engine, for example, various measurement principles are generally used. Besides the thermal measuring principles, at the basis of hot-film air mass meters (HFM), for example, air-mass measurements may be based on at least one pressure measurement. Mention is made here exemplarily of what are generally referred to as Prandtl probes or venturi tubes. To determine an air mass that flows through a tube per unit of time, for example, a differential pressure is measured from two static pressures or one static pressure and an absolute pressure. It is possible in these methods to enhance the accuracy of the air mass measurement, for example, by determining the density on the basis of additional pressure and/or temperature measurements.
German Patent Application No. DE 10 2014 212 854 A1, for example, describes a flowmeter for measuring a flow rate of a fluid medium that flows through a flow tube in a main flow direction. The flowmeter includes a disturbing element that partially narrows a flow cross section of the flow tube, a first pressure measuring point that is configured upstream of the disturbing element relative to the main flow direction, and a second pressure measuring point that is configured downstream of the disturbing element relative to the main flow direction. The disturbing element is designed for variably narrowing the flow cross-section of the flow tube.
German Patent Application No. DE 10 2007 053 273 A1 describes a flowmeter for measuring a flow rate of a fluid medium that flows through a flow tube in a main flow direction. The flowmeter features a connector part that has an incident flow side and an outflow side. Configured in the connector part on the inflow side is a stagnation chamber that is accessible on the inflow side through an opening. A first pressure measuring point is accommodated in a side wall of the stagnation chamber. A second pressure measuring point is configured in an outer wall of the connector part.
In spite of the advantages achieved using conventional measuring devices, there are still a multitude of technical challenges to overcome in the measurement of flow properties of fluid media. One challenge specifically encountered in the induction tract of internal combustion engines is to protect the sensors used from water and dirt particles and to thereby prevent the pressure sensors from providing an incorrect indication and, associated therewith, a faulty indication of the air mass.